I tend to dry some thicker soft maple in the 6/4 and 8/4 range. I have had problems with the boards ending up white on the outside, but grey in their cores. I keep my kiln temps below 107 (usually below 100 at first), and my RH well below 60% until the MC is below 20% then I raise the kiln to 120F. In addition to the two fans provided by nyle, I also added a 3' dia agricultural fan and three pontoon fans that I have set up blowing directly through the 5' wide lumber pile, yet still end up with the grey cores. I never overload the Nyle 200 either. I always keep the 6/4 and 8/4 loads to 500 bd ft, or less for at least a week before I add more (4/4 and 5/4). I had this problem throughout this past winter when the temps here were brutally cold as well as in the summer. I do not have this problem with my 4/4 and 5/4 maple. I read that 130 F kills the blue stain mold that I believe is the cause of this discoloration. Should I go off schedule and start the kiln at 130 F? It should also be noted that the lumber goes directly into the kiln from the mill. I have found that chemically spraying the lumber does little good. Thank You.